Protective system



. Nov. 5, 1963 D. W. FATH ETAL PROTECTIVE SYSTEM Filed March 10, 1958 (Hi 8 OFF 8 9 TEsT I0 T IZT 56 c7 58 I4T c IST 0 l 8 T o ZOT- 22 T 24 T j voLTAGE BEARING AaNoRNAL TEMPERATURE REGuLAToR MOTOR 110m 20 cIRcuIT KNIFE UV coNmTIoNs BREAKERS SWITCH RELAY Li '4 l2 10 24 22 I8 1? 1% Q L j NoToR sIIuNT- NoToR SHUNT AUTO To MANUAL 2| "-6 CIRCEIIT EAKER NNI F E G'TI ITGII TRANSFER SWITCHES AUXILIARY GENERATOR BEARING TENPERATIIRE RoIsT RIGIIT SKIP RELAY RIGHT SKIP sLowuovIN svIITcII /LINI|T sWITcII 50 34 36 LEFT SKIP sLoYIoowN y LINIT swITcII 5 4.

uv 38 4 REsET "I T- \-\HOIST LEFT SKIP RELAY sYIITcII 1' I 1 ll y A i I T 1 I I F I F I ovER- sLoYI FAST LEFT LEFT RIGIIT RIGIIT 52 SPEED SPEED SPEED SKIP SKIP SKIP SKIP GovER- RELAY RELAY OVER- GovER- ovER- GovER- NOR svIITcII swITcII TRAVEL NoR TRAVEL NOR o LINIT OVER- LINIT OVER- 48 swITcII TRAvEL SWITCH TRAVEL-O fii 4o 32 T 4 30 T o 28 T J) 2 TEsL OFF INVENTORS DOUQLAS W. FATH Attorney United States Patent 3,110,019 PRUTECTTVE SYSTEM D Douglas W. Fath, Brookticld, and Charles E. Smith, M lwaukee, Wis, assignors to Quilter-Hammer, line Milwaultee, Wis, a corporation of Delaware Filed Mar. 10, 1958, Ser. No. 7%,154 6 Claims. ill. Edd-213) This invention relates to improvements in electrical protective systems including fault finders, such as might be used with the electrical systems for the operation and control of ship hoist of a blast furnace charger.

Such system may be a so-called underv'oltage (hereafter designated UV) relay circuit for a skip hoist. Such UV relay circuit includes a number of contacts, circuit breakers, manually operated switches, and limit switches. if any one of these opens, it drops out a UV relay to stop the operation of the skip hoist and associated devices. Some of such contacts are relay controlled and open only momentarily and are monitored by a memory type annuciator. Some contacts are tied to manually operated knife switches used in closing motor field circuit and shunt brake circuits. Some of the circuit breakers operate in response to normal speed regulation and motor field conditions. Some contacts operate in response to D.C. generator bearing temperature, overload conditions, field loss, power conditions, and slack skip car cables. There are contacts which are opened in response to emergency stop requirements, such as failure of the skip car to slow .down near the end of its upward travel, or to stop when such car passes an ov ertravel point, or overspeed occurs. These latter contacts relate to movement of the skip car and failure to stop it can endanger human life and cause extensive damage to the skip hoist structure and other partsofthe blast furnace. These contacts will be called danger stop contacts. On the other hand, damage to the skip hoist motor and D.C. generator caused by overload or overheat is by comparison relatively less expensive and does not entail a danger element. These contacts will be referred to as protection contacts.

It is an object of this invention, therefore, to provide a protective system of this type which may include an emergency brake coil to release a biased quick stop brake on a skip hoist drum or other movable part upon opening of the danger stopcontacts and which will not so release on the opening of the protection contacts.

Another object of this invention is to provide such a protective system by which occurring malfunctions may be readily located.

This is accomplished by arranging the danger stop contacts in series between one side of the line and the UV relay contact and the protection contacts including the UV relay between such UV relay contact and the other side of the line. One fault finding selector switch is used to check the danger stop contacts and a second fault finding selector switch is used to check the protection contacts. This arrangement permits the incorporation of an emergency brake coil in series with the danger stop contacts and the other side of the line. Hence, when any of the danger stop contacts opens, the emergency brake coil will be immediately deener gized to trip a latch and release a biased brake and quickly stop movement of the skip car or other travelling part. The UV relay will also drop out and deenergize and normally stop the skip hoist or other prime mover. However, if any of the protective contacts open, the emergency brake :coil will not be deenergized and the skip hoist or other prime mover will come to a stop in the normal manner by the dropping out of the UV relay.

A specific embodiment of a protective system embodying fault finding in a UV relay circuit of a skip hoist shown in the schematic wiring diagram of the accompanying drawing. The skip cars, skip car cables, cable drum, emergency brake or skip hoist drum, limit switch cams operated by the cable drum shaft, governor, governor operated limit switch cams and other standard elements are not illustrated and are only briefly mentioned herein to provide background for the operation of the protective system. Skip hoist, as used herein, includes a D.C. generator and a skip hoist motor fed thereby. The skip hoist is operated as an adjustable voltage system with current limit acceleration and deceleration control.

Control of the skip hoist resides in an AC. powered control system which includes relay circuits operated by limit switches to govern normal operation and speed regulation and a constant D.C. powered control system including relay circuits energized by knife switches, relay contacts of relay circuits in the A.C. system and relay contacts of relay circuits in the mctoragenerator set armature and field circuits. The D.C. control system operates such items as dynamic braking con-tactors, motor contactors (directional control), brake contactors, field conrol contactors. Both control systems include contacts operated by the UV relay so that upon opening of such UV relay the skip hoist will make a normal stop. The D.C. power for the control system is supplied by a constant voltage exciter and power distribution system. which includes a motor-generator multipole transfer switch.

The UV relay circuit is placed across the same D.C. power line as the D.C. control system by a circuit breaker ii. This control circuit breaker should be open when opening or closing the motor and brake knife switches.

The UV relay circuit, starting from the negative side of the line includes in series in the order described the following components which are shown in the position assumed when the motor-generator set is opearting but not running the skip hoist, with one skip car in the skip car pit, and before energization of the UV relay circuit. A UV relay in enengizable to close its self-maintaining contact lila (shown open) and, when dropped out, causes the skip hoist to normally stop; a contact 12 interconnected with the motor brake knife switches; a contact 14 interconnected with the motor knife switches; contact 16 of a circuit breaker protecting the shunt field of the motor; a block group 18 of series connected contacts of circuit breakers in the voltage regulator circuit (not shown) by which normal speed is controlled; a contact 2% and a contact 21 responsive to the bearing temperature of the D.C. generators; switches 22 which are keyed in with motongenerator transfer switches; a block group of series connected contacts 24 some of which may be momentarily opened by corresponding relay circuits responsive to abnormal motor conditions such as over-voltage and overload of the generator and motor, loss of A.C. power, and motor field loss, others of which are opened by relay circuits responsive to slack conditions in' the skip car cable, and some of which are manually operable emergency stop button types, the controlling relay circuits may also operate memory type annunciators (not shown); and a block group as of contacts keyed to manually operated transfer switches used primarily to transfer from automatic to manual control including speed selection. This side or branch of the UV relay circuit thus groups the protector contacts between the negative side of the line and the UV contact 16a.

The UV relay circuit, starting from the positive side of the line, includes in series in the order described the following: contact 28 opened by an overspeed governor geared to the skip hoist cable; a group of contacts and limit switches used to check the slow down of the skip hoist near the upper end of its travel comprising a contact 3b which is open at the start of the skip hoist and later closes at the slow-down point under control of a slow speed relay circuit including a skip hoist cam operated limit switch, a contact 32 which is closed at the start of the skip hoist then opens as skip hoist speed is to be increased and later closes at the slow-down point under control of a fast speed relay circuit including a skip hoist cam operated limit switch, limit switches 34 and 36 one of which is closed at the start of the skip hoist in one direction and is opened a few feet (say less than after the slow-down point, and contacts 36 and it which alternate with change in direction of the skip hoist operation to place the proper one of limit switches 34 and 36 in shunt for contacts 34 and 32; limit switch 42 which opens it the left skip car travels beyond the final stop position; limit switch 44 which opens under control of the governor travel if the skip hoist drum continues to move in the same direction after the left skip car is at the upper end of its track; limit switch 4-6 which opens it the right skip car travels beyond the final stop position; and limit switch 48 which opens under control of the governor travel if the skip hoist drum continues to move in the same direction after the right skip car is at the upper end of its track. Thus, there is established a group or branch of danger stop contacts to open the UV relay circuit whenever the skip car is subject to overspeed, overtravel or failure to slow down before reaching the top. This group or branch of danger stop contacts is connected to the group or branch of protection contacts by the UV contact a. The UV relay it} is energized to close the UV relay circuit by a reset button switch 5t Which momentarily shunts the contact 10a.

With the aforedescribed arrangement and in circumstances where desirable it is possible (as shown) to connect an emergency brake coil 52 with the branch of danger stop contacts and the negative side of the line. This coil is energized under normal operating conditions and, when deenergized, will trip a latch of a spring biased 7 quick stop brake operating on the cable drum of the skip breaks the circuit to the UV relay iii and opens UV' contact 10a to break the UV relay circuit. In such assumed case the skip hoist, if then running, would stop in the normal manner by decreasing speed and braking. Now assume that the skip hoist car failed to reduce speed at the slow-down point because the slow speed relay circuit failed to drop out. The contact 3% would, therefore, remain open and, when the limit switch 34 or 36 (depending upon direction) opens as the skip hoist car passes beyond such slow-down point, the coil 52 will be deenergized causing fast stoppage by the emergency brake. At the same time the UV relay circuit will open to also normally stop the skip hoist.

As previously explained, some of the contacts have associated with them a memory type annunciator, however, it is advantageous and convenient to establish that a break has occurred at least in a block group consisting of such contacts. If the emergency brake stop has occurred because the slow speed relay failed to drop out, such condition is not apparent. The same stop could have been caused by a failure which opened any one of the contacts in the dangerous contact branch. Hence, a dual fault finding system is incorporated in the UV relay circuit. The negative side fault finding system checks the UV relay and the protection contacts from the negative side up to the UV relay contact itla. It com prises a test lamp 56 and selector switch 53 with at least 10 positions connected as shown. These positions include Oh for non-use, Test to see if the lamp 56 is functioning properly and positions corresponding in reference numeral with the component to be checked and distinguished by the added reference T. Selector switch 53 is moved from tap to tap in the clockwise direction and when lamp 56 fails to glow, the tap will indicate a faulty coil or designate the contact which has opened or subgroup of contacts at least one of which has opened. The first position in which the indicator lamp 56 does not glow indicates. by cross-reference the number of the component or group which has failed. In the case of the block groups '18, 24 and 26 the individual contacts or circuit breakers in such faulted group can be ascertained by its memory type annunciator or visible tripped position. Having thus ascertained the failed contact in the UV circuit, its corresponding relays, circuit breakers or other components in the control systems are thereby esignated and can be easily located for inspection and repair.

The positive side fault finding system checks the dangerous contacts from the positive side of the line up to the UV relay contact 10a. It comprises a test lamp on and selector switch 62 with 9 positions connected as shown and a spare position. These positions include Off for non-use, Test for checking the lamp 6t} and positions corresponding in reference numeral with the component to be checked and distinguished by added reference T. This selector switch is moved from tap to tap and when the lamp 6h fails to glow, the tap will designate the contact which has opened. This in turn will design-ate the tfailed part in the basic control systems or skip hoist operation.

It is advisable after any stoppage due to the dropping out of the UV relay to first attempt a reenergization by closing the reset button switch 50. If the stoppage was caused by a momentary opening of a self setting contact, there will be no need to use the fault finding selector switches.

We claim:

1. In an electrical protective system, an electrical power supply source, a protective relay, a first group of contacts connected in series circuit with one another and with the operating .coil of said relay to one side of said source, a second group of contacts connected in series circuit to the other side of said source, a contact on said relay operable when closed to connect said groups of contacts when closed to one another to complete a series circuit connection for said operating coil across said source, said first group of contacts being indicative of abnormal conditions requiring protection and opening of any contact in said first group causing deenergization of said relay operating coil, and a control device connected between the contacts of said second group and said one side of said source, and said second group of contacts being indicative of dangerous conditions and opening of any contact in said second group causing deenergization of both said control device and said relay operating coil.

2. The invention defined in claim 1, together with means for testing the operating condition of the contacts in each said group and for testing the operability of said relay operating coil.

3. The invention defined in claim 2, wherein said testing means comprises first means for progressively connecting the operating coil of said relay and the contacts of said first group across said power supply source to test the operability of said relay operating coil and the operating condition of the contacts in said first group thereof, and second means for progressively connecting the contacts of said second group across said power supply source to test the operating condition of each contact in said second group thereof.

4. The invention defined in claim 1, together with a normally open reset switch connected across said relay contact and being operable to complete the energizing circuit of said relay operating coil when said first and second groups of contacts are closed whereby to close said relay contact to maintain said operating coil energized. I

5. The invention defined in claim 4, together with testing means comprising first switch means for progressively connecting the operating coil of said relay and certain contacts and other subgroups of contacts of said first group to said other side of said source to test the operability of said relay operating coil and the operating condition of the contacts in said first group thereof, and second switch means for progressively connecting said contacts of said second group to said one side of said source to test the operating condition of each contact in said second group thereof thereby to determine the operability of said reset switch when the latter is closed.

.6. In a protective and testing system, an electrical power supply source, a protective relay, a first group of contacts connected in series circuit with'one another and with the operating coil of said relay to one side of said source, a second group of contacts connected in series circuit to the other side of said source, a normally open reset switch operable when closed to connect said groups of contacts when closed to one another to complete a series circuit connection for energizing said operating coil across said source, a normally open contact connected across said reset switch and being responsive to energization of said relay operating coil to maintain the latter energized after said reset switch is reopened, said first group of contacts being indicative of abnormal conditions requiring protection and opening of any contact in said first group causing ideenergization of said relay operating coil to afford protection against abnormal conditions, and a control device connected between said second group of contacts and said one side of said source, said second group of contacts being indicative of dangerous conditions and opening of any contact in said second group rendering said control device eliective to afford protection against dangerous conditions and causing deenergization of said relay operating coil, and testing means comprising a first selector switch connected between said other side of said source and spaced points in the first mentioned series circuit and being manually operable to check sequentially the operability of said relay operating coil and the closed condition of the contacts in said first group thereof, and a second selector switch connected between said one side of said source and spaced points in the second mentioned series circuit and being manually operable to check sequentially the closed condition 01f each contact in said second group thereof, and an indicator connected to each said selector switch for indicating the conditions being checked.

References Cited in the file of this patent UNITED STATES PATENTS 2,439,350 TarbOX Apr. 6, 1948 2,461,919 Powell Feb. 15, 1949 2,614,160 Foote et al. Oct. 14, 1952 2,736,009 Barnickel Feb. 21, 1956 OTHER REFERENCES The ABC of Large A.-C. Motor Control, published by Electric Machinery lMfig. Co., 1953, particularlypages 3, 4 and 5. 

1. IN AN ELECTRICAL PROTECTIVE SYSTEM, AN ELECTRICAL POWER SUPPLY SOURCE, A PROTECTIVE RELAY, A FIRST GROUP OF CONTACTS CONNECTED IN SERIES CIRCUIT WITH ONE ANOTHER AND WITH THE OPERATING COIL OF SAID RELAY TO ONE SIDE OF SAID SOURCE, A SECOND GROUP OF CONTACTS CONNECTED IN SERIES CIRCUIT TO THE OTHER SIDE OF SAID SOURCE, A CONTRACT ON SAID RELAY OPERABLE WHEN CLOSED TO CONNECT SAID GROUPS OF CONTACTS WHEN CLOSED TO ONE ANOTHER TO COMPLETE A SERIES CIRCUIT CONNECTION FOR SAID OPERATING COIL ACROSS SAID SOURCE, SAID FIRST GROUP OF CONTACTS BEING INDICATIVE OF ABNORMAL CONDITIONS REQUIRING PROTECTION AND OPENING OF ANY CONTACT IN SAID FIRST GROUP CAUSING DEENERGIZATION OF SAID RELAY OPERATING COIL, AND A CONTROL DEVICE CONNECTED BETWEEN THE CONTACTS OF SAID SECOND GROUP AND SAID ONE SIDE OF SAID SOURCE, AND SAID SECOND GROUP OF CONTACTS BEING INDICATIVE OF DANGEROUS CONDITIONS AND OPENING OF ANY CONTACT IN SAID SECOND GROUP CAUSING DEENERGIZATION OF BOTH SAID CONTROL DEVICE AND SAID RELAY OPERATING COIL. 